1. Field of the Invention
The present invention pertains to the art of adjustable roller bearings and, more particularly, to an adjustable roller bearing assembly for use in a machine tool.
2. Discussion of the Prior Art
Portable lathe type machine tools for use in machining pipes or other workpieces are widely known in the art. Such a lathe generally includes a first ring or frame member that is adapted to be fixedly secured about or onto a workpiece and a second ring member that is rotatable supported by the first ring member. The second ring member carries a tool carrier having a head adapted to receive and support a cutting tool element. The tool element can be advanced during operation of the lathe in order to perform a desired machining operation on the workpiece.
Various bearing arrangements are provided between tile relatively rotatable ring members of portable lathes, including sliding and roller type bearings. Sliding type bearings are exemplified by U.S. Pat. Nos. 4,754,672 and 4,665,782 which are both assigned to the assignee of the invention described herein. A roller type bearing is exemplified by U.S. Pat. No. 4,418,591 also assigned in common with the assignee of this invention. It is highly desirable in such bearing arrangements to make the bearings conveniently replaceable when they are damaged or worn, but more importantly it is highly desirable to make them adjustable to remove undesirable clearances and to equalize loading among the bearing elements. The ability to adjust the bearings enables one to compensate for wear of the bearings as well as manufacturing tolerances.
Various approaches have been made to provide adjustable roller bearing systems between the relatively rotatable elements of a portable lathe. U.S. Pat. No. 4,397,202, for example, discloses rotary bearing elements between the frame and a rotatable head of a portable lathe wherein the bearing elements are inclined relative to the axis of rotation of the rotatable head and are individually adjustable for rotation within a shaped trackway. U.S. Pat. No. 5,054,342 provides another example of an adjustable roller bearing arrangement between the rotatable tool carrying head of a portable lathe and the frame of the lathe. In accordance with U.S. Pat. No. 5,054,342, the position of individual roller bearings may be adjusted by an eccentric incorporated in a bolt element extending between the rotatable head and the frame of the portable lathe, and which also supports each roller bearing element. By releasing a threaded fastener engaging the bolt and rotating the eccentric stud, the radial position of the roller bearing may be adjusted relative to the fixed frame or the rotatable tool carrying head.
The broader concept of adjusting the position of a roller constituting part of a series of roller bearing elements to take up slack or remove clearances by providing an eccentric adjusting element on at least one of the bearing elements is well known in the art as exemplified by U.S. Pat. No. 3,661,431. FIG. 4, for example, of U.S. Pat. No. 3,661,431 illustrates an eccentric bushing that may be rotated to adjust the radial position of a roller element relative to a central shaft carrying the roller bearing and bushing. U.S. Pat. No. 4,011,670 shows still another arrangement for adjusting the position of a roller element relative to a fixed frame utilizing a support rod having an eccentric portion located at the location where the roller is mounted on the rod.
While the prior art adjustable roller bearing arrangements provide desirable adjustability of the position of the roller elements relative to the race or tracks with which they are associated, it is highly desirable to simplify the components required in an adjustable bearing arrangement by reducing the number of elements constituting the roller bearing support to thereby reduce inventory of parts required to manufacture the adjustable bearing assembly and to simplify the methodology by which the position of the bearings is adjusted after the bearings have been incorporated an a complete system, for example a machine tool such as a portable lathe.